I have an old Rheem A/C-Heat Pump Model RPFA-042JAS mfg'd in 1988. I know the unit should be replaced but I'm recently divorced and broke. Here's what's happening. When the unit is in heat mode, it makes a loud clicking noise. It sounds like it's coming from two places, the outside unit AND the inside air handler. I think it's a relay clicking but not sure. Any ideas?